This invention is related to machines used by humans to simulate practice with another human partner in the field of sports. In this case, the sport is table tennis.
Prior robots have been invented for sports such as tennis, table tennis, baseball and soccer. However, recycle systems have only been known to have been attempted for table tennis. At least one ball collecting system was invented for tennis (see U.S. Pat. No. 4,116,436, Bjorhn, 1978) but since the balls are not returned to a robot after collection, it is not considered to be a recycle system. U.S. Pat. No. 4,077,386 by Berliner in 1978 and some other robots employ a recycle system.
The convenience of a recycle system is desirable when practicing with a robot. However, at the present state of the art, recycle systems are lacking in their ability to permit the head of the robot to be positioned so that it can serve from various horizontal angles. Past recycle systems required the robot to be set in a fixed position relative to the table. This position was usually halfway between the table sides. If a recycle system returns balls to the robot via a flexible hose as in U.S. Pat. No. 4,765,618, the robot may be positioned at any suitable point between the table sides. This permits serves from various horizontal angles. Another way to do this is to omit a recycle system and feed the robot from a hopper. In the case of the hopper, it is part of the robot and therefore goes where the robot goes.
Although the hose system mentioned above works, it has inherent problems. The hopper also works, but there is no recycling.
Another problem on some earlier robots was jamming. The method of supplying balls to the head at a set rate was often achieved by rotating a notched wheel or perforated platter to convert from a multiplicity of balls to a single ball. The conversion allows successive single balls to be fed into the head. These methods often caused jamming because there is no guarantee that balls will fall into notches or perforations at the right time and place. The result is that balls sometimes get caught between fixed and moving surfaces of the ball container, thereby causing a jam.
Now, let us return to the problems encountered when a flexible hose is employed as a ball transportation path. In U.S. Pat. Nos. 4,559,918 and 4,765,618, the point-of-entry of balls returned to the system is a fixed trough or pan. The flexible hose permits variable lateral positioning of the robot""s head and a minimum hose length is required to cover positions over the entire width of the table.
The energy required to return balls to the head in the foregoing robots is supplied by an electric fan, which causes the balls to travel up the hose or tube under the force of air pressure or vacuum. The length of hose or tube and the airflow speed determine the recycle time of the system. This time is the time required to retrieve a returned ball and send it to the head. If this time is relatively long, the system is unable to keep up with the rate at which balls need to be served. This limitation can only be overcome by employing a more powerful energy source, which means a larger fan and more powerful motor. In practice, a more powerful source tends to be impractical because far more noise is generated and electrical energy requirement is highly increased.
Yet another problem with air feed systems, is that when the travel of balls up the hose or tube is not uniform, a situation sometimes arises where the balls pile up and inhibit further travel. This inhibition is due to the inability of the air supply to overcome the weight of a few balls at pile up. The result is that recycling ceases.
This invention permits the head of the robot to be placed at any position between the sides of the table without employing an air recycle system. Also, it eliminates jamming of the balls in the feed system. The mobility of the head allows the operator to receive serves from any angle and eliminates the need for a separate ball container.
The table tennis robot can be clamped to one end of the table at any available position between the sides of the table. A disk at the lower extremity of the robot forces the elastic bottom of the recycle net downward to form a conical trough at whatever position is chosen along the length of the net. Balls entering the recycle net enclosure are caught and roll down the incline of the trough, stopping on the disk. The balls are jostled about the disk by a rotating square platter and one by one they are lifted by an arm which is attracted by magnets affixed to a rotating wheel. This wheel clutches a lifted ball and carries it into a channel where it stops. When the wheel carries another ball it pushes the first ball further up the channel. The cycle continues and eventually the channel is filled with balls to the point where they arrive at the head of the robot. The head of the robot propels the balls one at a time onto the playing area so that a player can obtain practice. The rate at which the balls are propelled is dependent on the rotational speed of the wheel with magnets.
Provision is made for tilting the head of the robot to permit serves at different vertical angles. Also, the head of the robot may be oscillated in an arc of the horizontal plane and the height of the head maybe adjusted as desired.